Fuel cell, especially proton exchange membrane fuel cell (PEMFC), due to its multifaceted advantages, is one of the most promising alternative sources of energy. Bipolar plate is one of the key components of a fuel cell, which accounts for around 80% of the volume and 45%-60% of the stack cost. Traditional bipolar plate materials include graphite, metals and polymeric composites. Cost and technical limitation of traditional bipolar plate materials is one of the reasons that limits the large-scale commercialization of fuel cells. Graphite seems to be an ideal material for bipolar plate, but due to its brittleness, difficulties in mechanical processing of flow-field make it very expensive. Metallic plates have high electrical conductivity and excellent mechanical properties, but they are easy to be oxidized in acidic environment, which make the service life of metallic bipolar plate relatively short. Anti-corrosion coatings can be applied on metallic plate surface and enhance the overall corrosion resistance. U.S. Pat. No. 7,632,592 B2 discloses a method of applying a high-grade stainless steel or alloy corrosion-resistant coating on a low-grade stainless steel (304L or 316L) substrate plate by a kinetic spray process. U.S. Pat. No. 6,372,376 B1 discloses a method for enhancing the corrosion resistance by providing a corrosion-resistant polymer coating containing a plurality of electrically conductive, corrosion-resistant filler particles on the metallic substrate. While enhancing the corrosion resistance, these coatings can increase the contacting resistance or largely increase the cost.
A number of polymer/carbon fillers composites have also been developed as bipolar plate materials. U.S. Pat. No. 7,910,040 B2 discloses a method for preparing a bipolar plate composite material, in which vinyl ester works as binder and graphite powder, carbon nanotubes (CNTs), carbon fiber and modified organo clay work as conductive fillers, using a bulk molding compound process. Taherian et al. (2013) developed a sandwich-structured triple-filler bipolar plate composite material consisting of phenolic resin, graphite powder, expanded graphite, carbon fiber and a thin carbon fiber cloth. However, the electrical conductivity and flexural strength of the polymer/carbon but still, the filler composite cannot be well balanced. Researchers at Wuhan University of Technology developed an aluminate cement-graphite powder bipolar plate composite material, which has been proven to be of high-strength, highly conductive and low-cost. However, the structure of aluminate cement becomes unstable in acidic environment (<pH4), accompanied by the dissolution of metallic ions, such as Ca2+, Al3+, and so on, which will contaminate the proton exchange membrane and affect the performance of PEMFC.
Therefore, there is a need to develop a bipolar plate composite material with enhanced properties.